A process for removing heavy metal ions or cyanide ions from a waste water stream originating in a metal plating plant or a mine comprising the steps of pretreatment in which the waste water stream is first pretreated by removing particulates, fats and oils; filtration by means of a first sand filter to remove suspended particulates down to 50 microns, a second bag filter to remove suspended particulates down to 3.5 microns, a third micro filter to remove particulates down to 0.1 microns in size and a fourth ultrafilter to remove particulate down to a molecular weight of 10,000; concentration of the heavy metal ions in the waste water stream by means of a first stage nanofiltration unit and second stage nanofiltration unit or reverse osmosis membrane unit down to a molecular weight of about 200 with nanofiltration and less by reverse osmosis; increase the concentration of heavy metal species in the waste water stream to above 700 ppm; electrodialysis to further increase the concentration of heavy metal ions in the waste water stream to approximately 6000 ppm; electrolysis to remove heavy metal ions. Alternatively, ion exchange columns can be used to remove the heavy metal ions after the filtration and concentration in the nanofiltration membranes.

Plating waste water treatment and metals recovery system

A process and an apparatus for recovering a precious metal compound, in which the precious metal compound is separated from impurity metals by use of a reverse osmotic membrane, and the separated precious metal compound is recovered in a concentrated state through electrodialysis employing anion-exchange and cation-exchange membranes, whereby the precious metal compound in a process liquid can be recovered efficiently. When the recovered precious metal compound is added in the as-is form to precious metal plating solution, it is possible to control the plating solution.

Process and apparatus for recovery of precious metal compound

An apparatus and method for removing charged ions from solution by treating the solution with electrodialysis followed by Donnan dialysis. One of many applications is for treating the baths associated with the metal finishing, e.g. plating, anodizing, or etching, industry. For example, charged ions can be removed from the rinse baths of a plating line by treating the rinse water of a first rinse bath following the plating bath with an electrodialysis unit and returning the concentrated solution to the plating bath, and treating a second rinse bath following the first rinse bath with a Donnan dialysis unit to produce an additional concentrated solution and a diluted effluent which may be either discharged into a sewer or stream, or readily destroyed.

Method and apparatus for recovering charged ions from solution

A process for electrodialyzing ultrafiltrate and an electrodialysis cell for use in the process are disclosed. The ultrafiltrate contains ionic materials which form a deposit on at least one of the electrodes of the electrodialysis cell impairing the electrical efficiency of the cell. This problem is overcome by removing the deposited electrode from the cell while simultaneously replacing it with electrode relatively free of deposit, thereby restoring the electrical efficiency of the cell. The invention is particularly useful for treatment of the ultrafiltrate of an electrodeposition bath.

Treatment of ultrafiltrate by electrodialysis

In a preferred embodiment, plating chemicals are recovered from contaminated rinse water using an electrodialysis recovery unit immersed directly in an electroplating bath between a cathode intended to be plated and an anode. Electrodialysis is driven parasitically by the electroplating currents, thereby eliminating the cost of additional equipment dedicated solely for electrodialysis. The unit is sized and positioned so that only a relatively minor portion of the total plating current is employed for electrodialysis, thereby permitting a sufficiently high current density at the cathode to electrodeposit a dense, commercially acceptable metal plate.

Parasitic electrodialysis recovery of dissolved chemicals from dilute solutions directly into a plating bath

A method of recovering valuable metals from rinse baths associated with electroplating processes. The recovery utilizes electrodialysis to concentrate the metal to a sufficiently high concentration that convenient recovery of the metal, e.g., nickel or copper, can be completed by handling the metal as an ion in a liquid phase and without the need to plate the metal out on an electrode or precipitate it in any solid form.

Smith Jack D

Papers

Recovery of metal from rinse solutions

Verfahren zur entfernung von metall tragenden ionen aus ihrer relativ verduennten loesung und vorrichtung hierzu